The present invention relates to equipment for the extrusion of polyethyleneterephthalate.
Polyethyleneterephthalate (PET) is an extremely hygroscopic material; it is packaged and sold by manufacturers in the form of granules, with a degree of humidity equal to about 2,000 parts per million.
Before being able to be extruded, it is first dehumidified at 160xc2x0 C. for 6 hours, in order to eliminate the humidity internally and externally incorporated in each granule, up to 20 parts per million. Under these conditions, the material cannot be extruded without its hydrolyzing and so that it maintains a characteristic intrinsic viscosity.
Traditional dehumidification processes take place in most cases before the extrusion phase with single screws and prove to be complex and costly.
This traditional dehumidification process consists in keeping a quantity of material equal to the productive rate of the extruder (kg/hr), for 6 hours in a silo, and passing humidity-free air through it, with a considerable energy consumption.
Furthermore, it should be considered that, when PET comes from the recovery of ground post-consumption bottles and/or ground thin sheets deriving from waste products from the thermoforming of trays and blisters, dehumidification becomes particularly complex.
This material, in fact, over a temperature of 80xc2x0 C., tends to soften and, if it is not in granule form, as in this case, it conglomerates and can no longer be handled, unless its apparent weight is increased by means of an additional densification process.
The objective of the present invention is to produce equipment which overcomes the technical problems described above.
A further objective is to produce equipment which is particularly simple and with limited costs, which allows an optimum extrusion to be achieved.
An additional objective is obviously to be able to produce polyethyleneterephthalate (PET) without having to dehumidify and densify the ground product.
These objectives according to the present invention are achieved by producing equipment for the extrusion of Polyethyleneterephthalate which comprises a chassis (29), containing a co-rotating, oil-thermoregulated extruder with two screws (31, 32), which comprise a first zone (A), equipped with an opening (34) where there is an aspiration hood (35) for a first xe2x80x9copen topxe2x80x9d degassing, a second zone (C) where there is at least one stack (37, 35) for a further degassing, between the two zones (A,C) there being a tight zone (B), and a carrying and loading zone (E) activated by the screws (31,32).
The characteristics and advantages of a set of equipment for the extrusion of polyethyleneterephthalate according to the present invention can be more clearly understood from the following illustrative and non-limiting description.